Tunable interference filter, optical module, and electronic apparatus

ABSTRACT

A tunable interference filter includes: first and second opposed substrates; a first reflection film provided on a first reflection film fixing surface of the first substrate; a second reflection film provided on a second reflection film fixing surface of the second substrate and separated from the first reflection film by a gap; and a first electrode provided on a first electrode surface of the first substrate facing the second substrate, wherein the first electrode surface is spaced apart from the second substrate by a different distance than the first reflection film fixing surface, and a layered part in which the first reflection film and the first electrode are stacked is provided on the first electrode surface, the layered part being spaced apart from the second substrate by a larger distance than the first reflection film fixing surface.

BACKGROUND

1. Technical Field

The present invention relates to a tunable interference filter, anoptical module including the tunable interference filter, and anelectronic apparatus including the optical module.

2. Related Art

A tunable interference filter in which reflection films are respectivelyoppositely provided across a predetermined gap on surfaces opposed toeach other of a pair of substrates is known (for example, seeJP-A-2002-277758).

In the tunable interference filter disclosed in JP-A-2002-277758, thereflection layers are respectively provided on the opposed surfaces oftwo optical substrates, and capacitance electrodes are provided at theouter sides in the radial direction of the reflection layers on theopposed surfaces of the optical substrates. In the tunable interferencefilter, the capacitance electrodes opposed to each other act as anelectrostatic actuator, and a voltage is applied between the capacitanceelectrodes to vary the gap between the reflection layers by anelectrostatic attractive force.

In the tunable interference filter, an electric charge may accumulate onthe reflection layers, and, if the reflection layers opposed to eachother are respectively charged, an electrostatic force is generated.Accordingly, even in the case where a predetermined set voltage isapplied to the electrostatic actuator for setting the gap between thereflection layers to a set value, the gap may not be set to the desiredset value due to the electrostatic force on the charged reflectionlayers. In this case, there is a problem that it is difficult to extractlight having a desired wavelength from the tunable interference filter.

SUMMARY

An advantage of some aspects of the invention is to provide a tunableinterference filter, an optical module, and an electronic apparatus thatcan extract light having a desired wavelength with high accuracy.

An aspect of the invention is directed to a tunable interference filterincluding a first substrate, a second substrate opposed to the firstsubstrate, a first reflection film provided on a surface of the firstsubstrate facing the second substrate, a second reflection film providedon a surface of the second substrate facing the first substrate andopposed to the first reflection film across a gap between the reflectionfilms, and a first electrode provided on the surface of the firstsubstrate facing the second substrate, wherein the first substrate has afirst reflection film fixing surface provided with the first reflectionfilm, and a first electrode surface provided with the first electrode,the first electrode surface being spaced apart from the second substrateby a different distance than the first reflection film fixing surface,and a layered part in which the first reflection film and the firstelectrode are stacked is provided on the first electrode surface and isspaced apart from the second substrate by a larger distance than thefirst reflection film fixing surface.

According to the aspect of the invention, the layered part formed bystacking the first reflection film and the first electrode is spacedapart from the second substrate more than the first reflection filmfixing surface, and the first reflection film and the first electrodehave surface contact so they are electrically connected at the layeredpart. Thereby, even when the first reflection film is charged, theaccumulated charge may be released via the first electrode andgeneration of an electrostatic attractive force by charging between thefirst reflection film and the second reflection film may be prevented.

Here, it is conceivable that the edge of the first electrode and theedge of the first reflection film are brought into edge-to-edge contactfor conduction. However, in this case, the contact area is smaller andconduction reliability is lower, and thus, the charge of the firstreflection film may not be reliably released to the first electrode. Onthe other hand, as described above, by providing the layered part bystacking the first electrode and the first reflection film, the firstelectrode and the first reflection film may reliably be brought intosurface contact and become electrically connected.

Further, in the aspect of the invention, the layered part is provided onthe surface at a larger distance from the second substrate then thefirst reflection film fixing surface. Accordingly, the amount the gapbetween the reflection films and the gap between the electrodes may bevaried is not suppressed by the presence of the layered part. Therefore,the wavelength range that can be extracted by the tunable interferencefilter is not narrowed.

In the tunable interference filter of the aspect of the invention, it ispreferable that a second electrode is provided on the surface of thesecond substrate facing the first substrate and opposed to the firstelectrode via a larger gap between the first and second electrodes thanexists between the reflection films, and the layered part is formed byextending the first reflection film from the first reflection filmfixing surface over the first electrode surface and onto an innerperipheral edge of the first electrode.

In the tunable interference filter, a wavelength to be extracted bytransmission or reflection is determined by the gap between the firstreflection film and the second reflection film. Therefore, in thetunable interference filter, to acquire a transmitted or reflectedwavelength in response to a wider wavelength range, it is desirable towiden the variation range of the gap between the reflection films. Here,in the case where a voltage is applied between the first electrode andthe second electrode to vary the gap between the reflection films by anelectrostatic attractive force, if the gap between electrodes is smallerthan the gap between the reflection films, the gap between thereflection films may be varied only by the amount of the gap betweenelectrodes. In the configuration, the variation range of the gap betweenthe reflection films is smaller and the wavelength range that can beextracted by the tunable interference filter is narrower.

On the other hand, in the configuration described above, the gap betweenthe electrodes is formed to be larger than the gap between thereflection films, and thus, the gap between the reflection films may bechanged in a larger variation range, and the wavelength range that canbe extracted by the tunable interference filter is made wider.

Further, generally, an electrostatic attractive force acting between theelectrodes is inversely proportional to the square of distance, and, ifthe gap between the electrodes is smaller, control of the electrostaticattractive force becomes difficult and control of the gap between thereflection films becomes difficult. On the other hand, in theconfiguration described above, the gap between the electrodes is formedto be larger than the gap between the reflection films, and thus, thecontrol of the electrostatic attractive force is easier and the gapbetween the reflection films may be set to a desired value with highaccuracy.

In the tunable interference filter of the aspect of the invention, it ispreferable that the layered part is formed by stacking the firstreflection film on the first electrode.

In the configuration described above, the layered part has theconfiguration in which the first reflection film is stacked on the firstelectrode. That is, the first electrode is formed on the firstsubstrate, and then, the first reflection film is formed partly thereon.Here, if the first reflection film is formed on the first substratebefore the first electrode is formed, problems that the first reflectionfilm is easily deteriorated when the first electrode is formed, andresolution of the tunable interference filter is lower, may arise. Onthe other hand, by first forming the first electrode on the firstsubstrate, and then, forming the first reflection film thereon, thedeterioration of the first reflection film in the manufacturing processmay be suppressed. Therefore, the first reflection film having goodreflection characteristics may be formed, and reduction of resolution inthe tunable interference filter may be suppressed.

It is preferable that the tunable interference filter of the aspect ofthe invention includes a reflection film connection electrode connectedto the second reflection film.

In the configuration described above, since the reflection filmconnection electrode is connected to the second reflection film, thecharge accumulated in the second reflection film may be released fromthe reflection film connection electrode, and generation of anelectrostatic force between the first reflection film and the secondreflection film may be prevented more reliably. Therefore, the gapbetween the reflection films may be controlled with high accuracy bycontrolling the voltage applied to the first electrode and the secondelectrode.

Further, the reflection film connection electrode and the firstelectrode may be set at the same potential. In this case, noelectrostatic attractive force is generated between the first reflectionfilm and the second reflection film, and control of the gap between thereflection films may be performed easily with high accuracy.

Another aspect of the invention is directed to an optical moduleincluding the above described tunable interference filter, and adetection unit that detects light extracted by the tunable interferencefilter.

As described above, in the tunable interference filter of the aspect ofthe invention, even when the first reflection film is charged, thecharge may be released from the first electrode and no electrostaticforce is generated between the gap between the reflection films, and thedimension of the gap between the reflection films may accurately becontrolled. Thereby, in the tunable interference filter, a light havinga desired wavelength may be extracted by transmission or reflection withhigh accuracy. Further, in the optical module including the tunableinterference filter, by detecting the amount of the light having thedesired wavelength extracted by the tunable interference filter usingthe detection unit, the amount of the light having the desiredwavelength may accurately be detected.

In the optical module of the aspect of the invention, it is preferablethat the tunable interference filter includes a reflection filmconnection electrode connected to the second reflection film, and avoltage control unit is provided that controls the reflection filmconnection electrode and the first electrode at the same potential.

In the configuration described above, the voltage control unit sets thereflection film connection electrode connected to the second reflectionfilm and the first electrode at the same potential. Thereby, thepotential difference between the first reflection film and the secondreflection film is zero, and no electrostatic attractive force isgenerated between the first reflection film and the second reflectionfilm and the dimension of the gap between the reflection films may becontrolled with high accuracy.

Still another aspect of the invention is directed to an electronicapparatus including the above described optical module.

According to the aspect of the invention, the electronic apparatusincludes the optical module having the above described tunableinterference filter, and thus, various kinds of electronic processing inthe electronic apparatus may be performed based on the amount of thelight having the desired wavelength detected with high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a block diagram showing a schematic configuration of acolorimetric instrument of one embodiment according to the invention.

FIG. 2 is a plan view of a tunable interference filter of theembodiment.

FIG. 3 is a sectional view of the tunable interference filter of theembodiment.

FIG. 4 is a sectional view showing a schematic configuration of atunable interference filter of another embodiment.

FIG. 5 is a sectional view showing a schematic configuration of atunable interference filter of another embodiment.

FIG. 6 is a schematic diagram of a gas detector as another example of anelectronic apparatus according to the invention.

FIG. 7 is a block diagram of the gas detector in FIG. 6.

FIG. 8 is a block diagram showing a configuration of a food analyzer asanother example of the electronic apparatus according to the invention.

FIG. 9 is a schematic diagram of a spectroscopic camera as anotherexample of the electronic apparatus according to the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Below, one embodiment according to the invention will be explained withreference to the drawings.

1. Overall Configuration of Colorimetric Instrument

FIG. 1 is a block diagram showing a schematic configuration of acolorimetric instrument 1 (electronic apparatus) of the embodiment.

The colorimetric instrument 1 includes a light source unit 2 thatoutputs light to a test object A, a colorimetric sensor 3 (opticalmodule), and a control unit 4 that controls the operation of thecolorimetric instrument 1 as shown in FIG. 1. Further, the colorimetricinstrument 1 is a device that imparts light output from the light sourceunit 2 onto the test object A, receives the reflected test object lightin the colorimetric sensor 3, and analyzes and measures the chromaticityof the test object light, i.e., the color of the test object A based onthe detection signal output from the colorimetric sensor 3.

2. Configuration of Light Source Unit

The light source unit 2 includes a light source 21 and plural lenses 22(only one is shown in FIG. 1), and outputs white light to the testobject A. Further, the plural lenses 22 may include a collimator lens,and, in this case, the light source unit 2 collimates the white lightoutput from the light source 21 into parallel light by the collimatorlens and outputs it from a projection lens (not shown) toward the testobject A. Note that, in the embodiment, the colorimetric instrument 1including the light source unit 2 is exemplified, however, for example,in the case where the test object A is a light emitting member such as aliquid crystal panel, the light source unit 2 may be omitted.

3. Configuration of Colorimetric Sensor

The colorimetric sensor 3 includes a tunable interference filter 5, adetection unit 31 that receives light transmitted through the tunableinterference filter 5, and a voltage control unit 32 that varies thewavelength of the light to be transmitted through the tunableinterference filter 5 as shown in FIG. 1. Further, the colorimetricsensor 3 includes an incidence optical lens (not shown) that guides thereflected light (test object light) reflected on the test object Ainward in a location facing the tunable interference filter 5.Furthermore, the colorimetric sensor 3 spectroscopically separates alight having a predetermined wavelength of the test object lightsentering from the incidence optical lens by the tunable interferencefilter 5, and receives the spectroscopically separated light by thedetection unit 31.

The detection unit 31 includes plural photoelectric conversion elementsand generates electric signals in response to amounts of received light.Further, the detection unit 31 is connected to the control unit 4, andoutputs the generated electric signals as light reception signals to thecontrol unit 4.

3-1. Configuration of Tunable Interference Filter

FIG. 2 is a plan view showing a schematic configuration of the tunableinterference filter 5, and FIG. 3 is a sectional view showing theschematic configuration of the tunable interference filter 5.

The tunable interference filter 5 is a plate-like optical member havinga square shape in a plan view as shown in FIG. 2. The tunableinterference filter 5 includes a fixed substrate 51 (a first substrate)and a movable substrate 52 (a second substrate) as shown in FIG. 3. Thefixed substrate 51 and the movable substrate 52 are formed using variouskinds of glass of soda glass, crystalline glass, quartz glass, leadglass, potassium glass, borosilicate glass, alkali-free glass, orquartz. Further, the fixed substrate 51 and the movable substrate 52 areintegrally formed, in which a first bonding surface 513 and a secondbonding surface 523 formed near the outer peripheral parts are bondedusing a bonding film 53 formed by a plasma-polymerized film mainlycontaining siloxane, for example.

A fixed reflection film 54 forming a first reflection film is providedon the fixed substrate 51 and a movable reflection film 55 forming asecond reflection film is provided on the movable substrate 52. Here,the fixed reflection film 54 is fixed to the surface of the fixedsubstrate 51 facing the movable substrate 52, and the movable reflectionfilm 55 is fixed to the surface of the movable substrate 52 facing thefixed substrate 51. Furthermore, the fixed reflection film 54 and themovable reflection film 55 are oppositely provided spaced across a gapG1 between the reflection films.

In addition, an electrostatic actuator 56 for adjustment of thedimension of the gap G1 between the reflection films between the fixedreflection film 54 and the movable reflection film 55 is provided in thetunable interference filter 5. The electrostatic actuator 56 has a fixedelectrode 561 (a first electrode) provided at the fixed substrate 51side and a movable electrode 562 (a second electrode) provided at themovable substrate 52 side. Here, the fixed electrode 561 and the movableelectrode 562 may be provided directly on the substrate surfaces of thefixed substrate 51 and the movable substrate 52, respectively, or may beprovided via another film member.

Further, in a plan view (hereinafter, referred to as “plan view of thefilter”) of the tunable interference filter 5 as shown in FIG. 2 as seenfrom a substrate thickness direction of the fixed substrate 51 (movablesubstrate 52), the planar center point O of the fixed substrate 51 andthe movable substrate 52 coincides with the center points of the fixedreflection film 54 and the movable reflection film 55 and coincides withthe center point of a movable part 521, which will be described later.

3-1-1. Configuration of Fixed Substrate

The fixed substrate 51 is formed by processing a glass base materialformed in a thickness of 500 μm, for example. Specifically, on the fixedsubstrate 51, an electrode formation groove 511 and a reflection filmfixing part 512 are formed by etching as shown in FIG. 3. In the fixedsubstrate 51, a thickness dimension is formed larger than that of themovable substrate 52, and there is no electrostatic attractive forcewhen a voltage is applied between the fixed electrode 561 and themovable electrode 562 or deflection of the fixed substrate 51 due tointernal stress of the fixed electrode 561.

The electrode formation groove 511 is formed in an annular shape aroundthe planar center point O of the fixed substrate 51 in the plan view ofthe filter. The reflection film fixing part 512 is formed to projectfrom the center part of the electrode formation groove 511 toward themovable substrate 52 side in a plan view. Here, a groove bottom surfaceof the electrode formation groove 511 is a fixed electrode surface 511A(a first electrode surface) and a projecting end surface of thereflection film fixing part 512 is a reflection film fixing surface512A.

Further, three electrode lead grooves (not shown) extending from theelectrode formation groove 511 toward the respective apexes C1, C2, C3of the outer peripheral edge of the fixed substrate 51 are provided onthe fixed substrate 51.

The fixed electrode 561 having the annular shape around the planarcenter point O is formed on a fixed electrode surface 511A of the fixedsubstrate 51. Here, it is more preferable that the fixed electrode 561is formed in a circular ring shape. Further, the circular ring shapeincludes a configuration in which a fixed lead electrode 563 projectsfrom a part of the circular ring shape, a configuration in which a partof the circular ring is lost, and a nearly C-shaped configuration inwhich a part of the circular ring is divided.

Note that insulating films (not shown) for preventing discharge betweenthe fixed electrode 561 and the movable electrode 562 may be stacked onthe fixed electrode 561.

Further, the fixed lead electrode 563 extending from the outerperipheral edge of the fixed electrode 561 is formed on the fixedsubstrate 51. Specifically, the fixed lead electrode 563 is formed froma location of the outer peripheral edge of the fixed electrode 561nearest the apex C1 along the electrode formation groove extending inthe direction toward the apex C1 to the apex C1. The end part of thefixed lead electrode 563 (the part located on the apex C1 of the fixedsubstrate 51) forms a fixed electrode pad 563P.

Furthermore, a first opposed electrode 581 and a second opposedelectrode 582 are provided in the electrode lead grooves formed from theelectrode formation groove 511 toward the apexes C2, C3 of the fixedsubstrate 51, respectively. The first opposed electrode 581 and thesecond opposed electrode 582 are insulated from the fixed electrode 561.The end parts of the first opposed electrode 581 and the second opposedelectrode 582 (the parts located on the apexes C2, C3 of the fixedsubstrate 51) form a first opposed electrode pad 581P and a secondopposed electrode pad 582P, respectively.

As described above, the reflection film fixing part 512 is formed in anearly cylindrical shape having a diameter dimension smaller than thatof the electrode formation groove 511 coaxially with the electrodeformation groove 511, and the surface (projection end surface) of thereflection film fixing part 512 facing the movable substrate 52 is areflection film fixing surface 512A.

Here, as described above, the reflection film fixing part 512 is formedto project from the electrode formation groove 511 toward the movablesubstrate 52 side. Therefore, the reflection film fixing surface 512A islocated nearer the movable substrate 52 than the fixed electrode surface511A. That is, in the embodiment, the dimension of the gap G2 betweenelectrodes is formed larger than the dimension of the gap G1 between thereflection films.

Further, the electrode formation groove 511 and the reflection filmfixing part 512 are formed by etching (wet etching) one surface side ofthe fixed substrate 51, and thus, an outer circumference side surface512B of the reflection film fixing part 512 is not parallel to thesubstrate thickness direction of the fixed substrate 51, but has acurved shape gently curved from the reflection film fixing surface 512Atoward the fixed electrode surface 511A.

Furthermore, the fixed reflection film 54 is formed to cover thereflection film fixing surface 512A, the outer circumference sidesurface 512B, and the inner circumference part of the ring-shaped fixedelectrode 561 provided on the fixed electrode surface 511A. Here, thepart in which the fixed reflection film 54 and the fixed electrode 561are stacked forms a layered part 57. The fixed reflection film 54 isformed in a circular shape around the planar center point O in the planview of the filter as shown in FIG. 2. Therefore, the layered part 57has a ring shape along a virtual circle around the planar center pointO.

As the fixed reflection film 54, a conductor material may be used. As aconductor material film, for example, a single-layer film of Ag or Agalloy may be used. In the case of a dielectric multilayer film, forexample, a dielectric multilayer film with a high-refractive-index layerof TiO₂ and a low-refractive-index layer of SiO₂ may be used.

The fixed reflection film 54 is in surface contact with the fixedelectrode 561 by the layered part 57 and electric conduction with thefixed electrode 561. Thereby, even when the fixed reflection film 54 ischarged, the accumulated charge can be released to the fixed electrode561. Further, in the case where a film formed by stacking a dielectricfilm as an insulator and a multilayer film thereof on a metal film isused as the fixed reflection film 54, the metal film and the fixedelectrode 561 have direct contact and electric conduction at least inthe surface contact part with the fixed electrode 561 in the layeredpart 57. Thereby, even when the fixed reflection film 54 is charged, thecharge accumulated near the metal film and the interface between themetal film and the insulating film can be released to the fixedelectrode 561.

Further, in the fixed substrate 51, an anti-reflection film (not shown)is formed in a location corresponding to the fixed reflection film 54 onthe opposite surface to the movable substrate 52. The anti-reflectionfilm is formed by alternately stacking a low-refractive-index film and ahigh-refractive-index film for reducing reflectance and increasingtransmittance of visible light on the surface of the fixed substrate 51.

3-1-2. Configuration of Movable Substrate

The movable substrate 52 is formed by processing a glass base materialformed in a thickness of 200 μm, for example, by etching.

Specifically, the movable substrate 52 includes a movable part 521having a circular shape around the planar center point O and a holdingpart 522 that is coaxial with the movable part 521 and holds the movablepart 521 in the plan view of the filter as shown in FIG. 2.

Further, the movable substrate 52 has cutout parts 524 in correspondencewith the respective apexes C1, C2, C3 of the fixed substrate 51, and thefixed electrode pad 563P, the first opposed electrode pad 581P, and thesecond opposed electrode pad 582P are exposed on the surface of thetunable interference filter 5 as seen from the movable substrate 52 sideas shown in FIG. 2.

The movable part 521 is formed to have a thickness dimension larger thanthat of the holding part 522, and, for example, in the embodiment,formed to have the same dimension of 200 μm as the thickness dimensionof the movable substrate 52. Further, the movable part 521 is formed tohave at least a larger radial dimension than the radial dimension of theouter peripheral edge of the fixed electrode 561. The surface of themovable part 521 facing the fixed substrate 51 is a movable surface 521Aparallel to the reflection film fixing surface 512A, and the movablereflection film 55 opposed to the fixed reflection film 54 via the gapG1 between the reflection films and the movable electrode 562 opposed tothe fixed electrode 561 via the gap G2 between electrodes are fixed tothe movable surface 521A.

For the movable reflection film 55, a reflection film having the sameconfiguration as that of the above described fixed reflection film 54 isused. Further, a reflection film connection electrode 551 extending fromthe outer peripheral edge of the movable reflection film 55 is formed onthe movable substrate 52. The reflection film connection electrode 551is formed from a location of the outer peripheral edge of the movablereflection film 55 nearest the apex C2 toward the apex C2. As thereflection film connection electrode 551, an electrode havingconductivity may be used. If the movable reflection film 55 is made of aconducting metal such as a silver alloy, for example, the same materialas that of the movable reflection film 55 may be used and the reflectionfilm connection electrode 551 may be patterned at formation of themovable reflection film 55. Further, a member that is different from themovable reflection film 55 may be used, and, in this case, thereflection film connection electrode 551 is formed by the same materialas that of the movable electrode 562, for example, and thus, thereflection film connection electrode 551 may be patterned at formationof the movable electrode 562.

Further, the reflection film connection electrode 551 is electricallyconnected to the first opposed electrode 581 (first opposed electrodepad 581P) formed in the location of the apex C2 of the fixed substrate51 near the outer peripheral edge of the movable substrate 52 by aconducting member 58 of Ag paste or the like, for example. Thereby, thecharge of the movable reflection film 55 can be eliminated from thefirst opposed electrode pad 581P located on the apex C2 of the fixedsubstrate 51.

The movable electrode 562 provided on the movable surface 521A is formedin a region overlapping with the fixed electrode 561 and in a C shapehaving a part corresponding to the apex C2 opening in a plan view of thefilter. The reflection film connection electrode 551 is formed towardthe apex C2 in the C-shaped opening part. Further, the width dimensionof the movable electrode 562 is formed in the same dimension as the ringwidth dimension (the difference between the radius of the innercircumferential edge and the radius of the outer circumferential edge)of the fixed electrode 561.

Further, a movable lead electrode 564 extending from the outercircumferential edge of the movable electrode 562 is formed on themovable substrate 52. The movable lead electrode 564 extends from alocation of the movable electrode 562 nearest the apex C3 toward theapex C3. The movable lead electrode 564 is electrically connected to thesecond opposed electrode 582 (second opposed electrode pad 582P) formedin the location of the apex C3 of the fixed substrate 51 near the outerperipheral edge of the movable substrate 52 by a conducting member of Agpaste or the like, for example.

Furthermore, in the movable part 521, an anti-reflection film (notshown) is formed on the opposite surface to the fixed substrate 51. Theanti-reflection film has the same configuration as that of theanti-reflection film formed on the fixed substrate 51 and is formed byalternately stacking a low-refractive-index film and ahigh-refractive-index film.

The holding part 522 is a diaphragm surrounding the movable part 521,and formed in a thickness dimension of 50 μm, for example, and having astiffness that is smaller than that of the movable part 521 in thethickness direction.

Accordingly, the holding part 522 is more likely to deflect than themovable part 521, and may be deflected toward the fixed substrate 51side by a small electrostatic attractive force. In this regard, sincethe movable part 521 has a larger thickness dimension and largerstiffness than those of the holding part 522, even when a force ofdeflecting the movable substrate 52 acts thereon by the electrostaticattractive force, there is little deflection of the movable part 521 andthe deflection of the movable reflection film 55 formed in the movablepart 521 may be prevented.

Note that, although the holding part 522 having the diaphragm shape isexemplified in the embodiment, the shape is not so limited. For example,a holding part having beam shapes provided at equal angular intervalsaround the planar center point O may also be employed.

3-2. Configuration of Voltage Control Unit

The voltage control unit 32 is connected to the fixed electrode pad563P, the first opposed electrode pad 581P, and the second opposedelectrode pad 582P, sets the fixed electrode pad 563P, the first opposedelectrode pad 581P, and the second opposed electrode pad 582P atpredetermined potentials based on the control signal input from thecontrol unit 4, and thereby, applies a voltage to the electrostaticactuator 56 for driving.

Specifically, the voltage control unit 32 grounds the first opposedelectrode pad 581P and the fixed electrode pad 563P, and sets apotential for setting the gap G1 between the reflection films to apredetermined dimension for the second opposed electrode pad 582P.Thereby, a voltage is applied between the fixed electrode 561 connectedto the fixed electrode pad 563P and the movable electrode 562 connectedto the second opposed electrode pad 582P, the movable part 521 moves tothe fixed substrate 51 side by the electrostatic attractive force, andthe dimension of the gap G1 between the reflection films is set to apredetermined value. In this regard, both the first opposed electrodepad 581P and the fixed electrode pad 563P are grounded, and thus, evenwhen the fixed reflection film 54 and the movable reflection film 55 arecharged, the charge may be released and no electrostatic attractiveforce acts between the fixed reflection film 54 and the movablereflection film 55. Therefore, for setting the gap G1 between thereflection films, the gap G1 between the reflection films may be set toa desired target value with high accuracy only by setting the voltagebetween the fixed electrode 561 and the movable electrode 562 withoutconsideration of the electrostatic attractive force acting between thefixed reflection film 54 and the movable reflection film 55.

Note that, in the embodiment, the first opposed electrode pad 581P andthe fixed electrode pad 563P are grounded, however, a configuration inwhich a predetermined potential can be set may be employed. In thiscase, the potential difference between the set potential of the secondopposed electrode pad 582P and the set potential of the fixed electrodepad 563P is applied to the electrostatic actuator 56 as a drive voltage,and thereby, the dimension of the gap G1 between the reflection filmsmay be controlled. Further, in this case, by setting the first opposedelectrode pad 581P and the fixed electrode pad 563P at the samepotential, the fixed reflection film 54 and the movable reflection film55 may be at the same potential and the electrostatic attractive forcein the gap G1 between the reflection films may be eliminated.

Further, the voltage control unit 32 may ground the second opposedelectrode pad 582P and set potentials for driving the electrostaticactuator 56 for the first opposed electrode pad 581P and the fixedelectrode pad 563P. In this case, the voltage control unit 32 may drivethe electrostatic actuator 56 by the applied voltage based on thepotentials set for the first opposed electrode pad 581P and the fixedelectrode pad 563P. In addition, the same potential is set for the firstopposed electrode pad 581P and the fixed electrode pad 563P, andthereby, no electrostatic attractive force acts between the fixedreflection film 54 and the movable reflection film 55, and the gap G1between the reflection films may be controlled with high accuracy by thepotential set for the first opposed electrode pad 581P and the fixedelectrode pad 563P.

4. Configuration of Control Unit

The control unit 4 controls the operation of the colorimetric instrument1.

As the control unit 4, for example, a general-purpose personal computer,a portable information terminal, and additionally, acolorimetry-dedicated computer or the like may be used.

Further, the control unit 4 includes a light source control part 41, acolorimetric sensor control part 42, a colorimetric processing part 43(an analytical processing unit) as shown in FIG. 1.

The light source control part 41 is connected to the light source unit2. Further, the light source control part 41 outputs a predeterminedcontrol signal to the light source unit 2 based on the setting input bya user, for example, and allows the light source unit 2 to output whitelight with predetermined brightness.

The colorimetric sensor control part 42 is connected to the colorimetricsensor 3. Further, the colorimetric sensor control part 42 sets thewavelength of light to be received by the colorimetric sensor 3 based onthe setting input by the user, for example, and outputs a control signalfor detecting the amount of received light having the wavelength to thecolorimetric sensor 3. Thereby, the voltage control unit 32 of thecolorimetric sensor 3 sets the voltage applied to the electrostaticactuator 56 so that only the wavelength of the light desired by the usermay be transmitted based on the control signal.

The colorimetric processing part 43 analyzes the chromaticity of thetest object A from the amount of received light detected by thedetection unit 31.

5. Advantages of Embodiment

As described above, in the tunable interference filter 5 according tothe embodiment, the fixed substrate 51 has the fixed electrode surface511A and the reflection film fixing surface 512A at different distancesfrom the movable substrate 52, and the fixed electrode 561 is providedon the fixed electrode surface 511A, and the fixed reflection film 54 isprovided from the reflection film fixing surface 512A over part of thefixed electrode surface 511A. Further, the outer circumference part ofthe fixed reflection film 54 is stacked on the inner circumference partof the fixed electrode 561, and the stacked structure forms the layeredpart 57. Accordingly, in the layered part 57, the fixed reflection film54 and the fixed electrode 561 have surface contact and the fixedreflection film 54 and the fixed electrode 561 are electricallyconnected, and, even when the fixed reflection film 54 is charged, thecharge may be released from the fixed electrode 561. Therefore, thegeneration of electrostatic force by the charging the fixed reflectionfilm 54 and the movable reflection film 55 may be prevented, andadjustment of the dimension of the gap G1 between the reflection filmsby the voltage control unit 32 may easily be performed with highaccuracy.

In this regard, in the layered part 57, by the surface contact betweenthe fixed reflection film 54 and the fixed electrode 561, conductionbetween the fixed reflection film 54 and the fixed electrode 561 mayreliably be secured, and the charge of the fixed reflection film 54 maybe released to the fixed electrode 561. Further, the thickness dimensionof the layered part 57 becomes larger than those of the fixed reflectionfilm 54 and the fixed electrode 561 by stacking the fixed reflectionfilm 54 and the fixed electrode 561. However, the layered part 57 isprovided on the fixed electrode surface 511A at a larger distance fromthe movable substrate 52, and thus, the variable range of the gap G1between the reflection films may not be hindered by the thickness of thelayered part 57 and the variable region of the gap G1 between thereflection films may sufficiently be secured.

Further, in the fixed substrate 51, the reflection film fixing surface512A is formed to project from the fixed electrode surface 511A towardthe movable substrate 52 side and the dimension of the gap G2 betweenelectrodes is larger than the dimension of the gap G1 between thereflection films. Accordingly, the variable region of the gap G1 betweenthe reflection films may be made larger, and the measurable wavelengthrange of the colorimetric instrument 1 may be made wider. In addition,the control of the electrostatic attractive force between the fixedelectrode 561 and the movable electrode 562 may be easier and thedimension of the gap G1 between the reflection films may be set to adesired value with higher accuracy.

Furthermore, in the layered part 57, the fixed reflection film 54 isstacked on the fixed electrode 561. During manufacturing, the tunableinterference filter 5 may be easily formed by depositing the fixedelectrode 561, and then, depositing the fixed reflection film 54. Sincethe fixed reflection film 54 is formed after the fixed electrode 561,damage of the fixed reflection film 54 during manufacturing may besuppressed.

In addition, the reflection film connection electrode 551 is connectedto the movable reflection film 55 and the reflection film connectionelectrode 551 is connected to the voltage control unit 32 from the firstopposed electrode pad 581P and grounded. Accordingly, even when themovable reflection film 55 is charged, the charge may be released fromthe reflection film connection electrode 551 and generation of theelectrostatic force between the fixed reflection film 54 and the movablereflection film 55 may be prevented more reliably.

Further, the potential set for the first opposed electrode pad 581P andthe fixed electrode pad 563P is not limited to the zero potential aslong as the first opposed electrode pad 581P and the fixed electrode pad563P are at the same potential by the voltage control unit 32. In thiscase, the fixed reflection film 54 and the movable reflection film areat the same potential, and the generation of electrostatic attractiveforce between the fixed reflection film 54 and the movable reflectionfilm 55 may be prevented.

Modifications of Embodiment

Note that the invention is not limited to the above describedembodiment, but includes modifications, improvements, and the likewithin the range in which the purpose of the invention may be achieved.

For example, in the embodiment, the example in which the first substrateis the fixed substrate 51 and the fixed electrode surface 511A and thereflection film fixing surface 512A formed in different height locationsare provided on the fixed substrate 51 has been shown, however, aconfiguration with the first substrate as the movable substrate 52 asshown in FIG. 4 may be employed.

FIG. 4 is a sectional view showing a schematic configuration of atunable interference filter 5A in another embodiment.

As shown in FIG. 4, the tunable interference filter 5A includes thefixed substrate 51 and the movable substrate 52.

The fixed substrate 51 includes the electrode formation groove 511having the fixed electrode surface 511A and the reflection film fixingpart 512 having the reflection film fixing surface 512A. Here, unlikethe above described embodiment, the fixed electrode 561 and reflectionfilm 54 are independently provided on the fixed electrode surface 511Aand the reflection film fixing surface 512A, respectively. Further,although not illustrated, the fixed electrode 561 is formed in a nearlyC-shape in the plan view of the filter, and the reflection filmconnection electrode connected to the fixed reflection film 54 is formedto extend toward the apex of the colorimetric instrument 1 of the fixedsubstrate 51 (for example, the apex C2 in FIG. 2) in the C-shapedopening part.

On the other hand, the movable substrate 52 has a projection part 525projecting from the movable part 521 toward the fixed substrate 51 sideand an electrode formation concave part 526. Here, the projection endsurface (projection surface 525A) of the projection part 525 forms afirst reflection film fixing surface, a bottom surface 526A of theelectrode formation concave part 526 forms a first electrode surface,and a distance of the bottom surface 526A from the fixed substrate 51 isformed larger than that of the projection surface 525A.

Further, the movable electrode 562 opposed to the fixed electrode 561via the gap G2 between electrodes is provided in a location overlappingwith the fixed electrode 561 in the plan view of the filter.Furthermore, the movable reflection film 55 opposed to the fixedreflection film 54 via the gap G1 between the reflection films isprovided on the projection surface 525A, and the movable reflection film55 is provided from the projection surface 525A over a part of thebottom surface 526A. The outer circumference part of the movablereflection film 55 is stacked on the inner circumference part of themovable electrode 562 and forms a layered part 57A.

In the tunable interference filter 5A, like the above described tunableinterference filter 5, even when the movable reflection film 55 ischarged, the charge may be released to the movable electrode 562.Further, even when the fixed reflection film 54 is charged, the chargemay be released by the reflection film connection electrode. Therefore,no electrostatic attractive force acts between the fixed reflection film54 and the movable reflection film 55, and the dimension of the gap G1between the reflection films may be set with high accuracy bycontrolling the voltage applied between the fixed electrode 561 and themovable electrode 562.

Further, in the embodiment and the example shown in FIG. 4, the examplein which the pair of opposed electrodes (the fixed electrode 561 and themovable electrode 562) form the electrostatic actuator 56 has beenshown, however, as shown in FIG. 5, a configuration in which pluralelectrodes form the electrostatic actuator 56 may be employed. FIG. 5 isa sectional view showing a schematic configuration of a tunableinterference filter 5B of another embodiment.

In the tunable interference filter 5B shown in FIG. 5, an inner movableelectrode 562A and an outer movable electrode 562B form the movableelectrode 562. In the tunable interference filter 5B, by individuallycontrolling the voltage applied between the inner movable electrode 562Aand the fixed electrode 561 and the voltage applied between the outermovable electrode 562B and the fixed electrode 561, the amount ofdisplacement of the movable part 521 may be set with higher accuracy.

Further, in the embodiment, as shown in FIG. 3, the example in which thereflection film fixing surface 512A of the reflection film fixing part512 opposed to the movable substrate 52 is located nearer the movablesubstrate 52 than the fixed electrode surface 511A and the dimension ofthe gap G2 between electrodes is larger than the gap G1 between thereflection films has been shown, however, the configuration is not solimited. The height locations of the fixed electrode surface 511A andthe reflection film fixing surface 512A may be appropriately setdepending on the wavelength range of the light to be transmitted by thetunable interference filter 5 (measurement wavelength range), i.e., thevariable range of the gap G1 between the reflection films, the dimensionof the gap G2 between electrodes, the thickness dimensions of the fixedreflection film 54 and the movable reflection film 55. Therefore, forexample, a configuration in which a reference film fixing groove havinga cylindrical recessed groove shape is formed in the center part of thefixed electrode surface 511A and a reference film fixing surface isformed on the bottom surface of the reference film fixing groove may beemployed. In this case, the layered part 57 in which the fixedreflection film 54 and the fixed electrode 561 are stacked is providedin the bottom surface part of the reference film fixing groove at thelarger distance from the movable substrate 52, and thereby, theinconvenience that the variable amount of the gap G2 between electrodesis restricted by the thickness dimension of the layered part 57 may beavoided.

Further, in the embodiment, the fixed electrode 561 forming theelectrostatic actuator 56 has been exemplified as the first electrode,however, the configuration is not so limited. For example, a chargeelimination electrode for eliminating the charge of the fixed reflectionfilm 54 may be formed on the fixed electrode surface 511A of the fixedsubstrate 51 and the fixed reflection film 54 may be stacked on thecharge elimination electrode for eliminating the charge.

Furthermore, in the example shown in FIG. 4, the fixed reflection film54 is connected to the reflection film connection wire (not shown) andthe charge is eliminated from the reflection film connection wire,however, for example, a configuration in which a charge eliminationelectrode is formed on the fixed electrode surface 511A of the fixedsubstrate 51 and the fixed reflection film 54 is stacked on the chargeelimination electrode may be employed. In this case, a layered structureof the charge elimination electrode and the fixed reflection film 54 isformed on the fixed electrode surface 511A at the larger distance fromthe movable substrate 52 than the reflection film fixing surface 512Aand the variable range of the gap G1 between the reflection films doesnot become narrower by the thickness of the layered structure, and thecharge may be released more reliably even when the fixed reflection film54 is charged by surface contact between the charge eliminationelectrode and the fixed reflection film 54.

In the embodiment and the examples shown in FIGS. 4 and 5, theconfiguration in which the gap G2 between electrodes is larger than thegap G1 between the reflection films has been exemplified, however, forexample, a configuration in which the gap G2 between electrodes issmaller than the gap G1 between the reflection films may be employed. Inthis case, the variable range of the gap G1 between the reflection filmsis restricted by the gap G2 between electrodes, however, the restrictionis not problematic when a sufficient dimension is secured for thewavelength range to be measured. Note that, as described above, theelectrostatic attractive force is larger in inverse proportion to thesquare of distance, and, as the distance of the gap G2 betweenelectrodes is smaller, the control of the gap G1 between the reflectionfilms becomes difficult.

Further, the layered part 57 has been formed by stacking the fixedreflection film 54 on the fixed electrode 561, however, a configurationin which the fixed electrode 561 is stacked on the fixed reflection film54 may be employed.

In this case, if a material that easily deteriorates such as a silveralloy is used as a fixed reflection film 54, for example, deteriorationmay occur during formation of the fixed electrode 561 after formation ofthe fixed reflection film 54. For example, by masking the formed fixedreflection film 54 or otherwise, the number of steps increases, but thedeterioration may be suppressed. Further, in the case where the fixedreflection film 54 is deteriorated, the deterioration usually progressesfrom the outer circumferential edge, however, in the configuration inwhich the outer circumferential edge of the fixed reflection film 54 iscovered by the fixed electrode 561, the progress of deterioration of thefixed reflection film 54 may be suppressed.

The colorimetric instrument 1 has been exemplified as an electronicapparatus according to the invention, however, the tunable interferencefilter, the optical module, and an electronic apparatus according to theinvention may be used in other various fields.

For example, they may be used as a light-based system for detecting thepresence of a specific material. As the system, for example, a gasdetector such as a vehicle-mounted gas leak detector that detects aspecific gas with high sensitivity by employing a spectroscopicmeasurement method using the tunable interference filter according tothe invention or a photoacoustic gas detector for a breath test may beexemplified.

Below, an example of the gas detector will be explained according to thedrawings.

FIG. 6 is a schematic diagram showing an example of a gas detectorincluding the tunable interference filter.

FIG. 7 is a block diagram showing a configuration of a control system ofthe gas detector in FIG. 6.

This gas detector 100 includes a sensor chip 110, a channel 120 having asuction port 120A, a suction channel 120B, an eject channel 120C, and aneject port 120D, and a main body part 130 as shown in FIG. 6.

The main body part 130 includes a detector (optical module) having asensor part cover 131 having an opening in which the channel 120 isdetachable, an ejecting unit 133, a housing 134, an optical unit 135, afilter 136, the tunable interference filter 5, a light receiving device137 (detection unit), a control unit 138 that processes a detectedsignal and controls the detection unit, a power supply unit 139 thatsupplies power, and the like. Further, the optical unit 135 includes alight source 135A that outputs light, a beam splitter 135B that reflectsthe light entering from the light source 135A toward the sensor chip 110side and transmits the light entering from the sensor chip side to thelight receiving device 137 side, and lenses 135C, 135D, 135E. Althoughthe configuration using the tunable interference filter 5 isexemplified, configurations using the above described tunableinterference filters 5A, 5B may be employed.

Further, as shown in FIG. 7, on the surface of the gas detector 100, anoperation panel 140, a display unit 141, a connection part 142 forinterface with the outside, and the power supply unit 139 are provided.If the power supply unit 139 is a secondary cell, a connection part 143for charging may be provided.

Furthermore, as shown in FIG. 7, the control unit 138 of the gasdetector 100 includes a signal processing part 144 having a CPU, alightsource driver circuit 145 for control of the light source 135A, avoltage control part 146 for control of the tunable interference filter5, a receiver circuit 147 that receives a signal from the lightreceiving device 137, a sensor chip detector circuit 149 that receives asignal from a sensor chip detector 148 that detects presence or absenceof the sensor chip 110, an eject driver circuit 150 that controls theejecting unit 133, and the like.

Next, an operation of the gas detector 110 will be explained.

Inside of the sensor part cover 131 in the upper part of the main bodypart 130, the sensor chip detector 148 is provided and presence orabsence of the sensor chip 110 is detected by the sensor chip detector148. When the signal processing part 144 detects the detection signalfrom the sensor chip detector 148, the part determines that the state inwhich the sensor chip 110 is mounted, and outputs a display signal tothe display unit 141 for displaying that a detection operation can beperformed.

Then, for example, if the operation panel 140 is operated by a user andan instruction signal of starting detection processing is output fromthe operation panel 140 to the signal processing part 144, first, thesignal processing part 144 outputs a signal of light source activationto the light source driver circuit 145 and activates the light source135A. When the light source 135A is driven, a stable laser beam oflinearly-polarized light having a single waveform is output from thelight source 135A. Further, a temperature sensor and a light amountsensor are contained in the light source 135A, and their information isoutput to the signal processing part 144. Then, if the signal processingpart 144 determines that the light source 135A is in stable operationbased on the temperature and the light amount input from the lightsource 135A, the part controls the eject driver circuit 150 to activatethe ejecting unit 133. Thereby, a gas sample containing a targetmaterial (gas molecules) to be detected is guided from the suction port120A into the suction channel 120B, the sensor chip 110, the ejectchannel 120C, and the eject port 120D.

The sensor chip 110 has plural metal nanostructures incorporated thereinand uses localized surface plasmon resonance. In the sensor chip 110,when enhanced electric fields are formed between the metalnanostructures by the laser beam and the gas molecules enter theenhanced electric fields, Raman scattering light and Rayleigh scatteringlight containing information of molecule oscillation are generated.

The Raman scattering light and Rayleigh scattering light enter thefilter 136 through the optical unit 135, the Rayleigh scattering lightis separated by the filter 136, and the Raman scattering light entersthe tunable interference filter 5. Then, the signal processing part 144controls the voltage control part 146 to adjust the voltage applied tothe tunable interference filter 5 and allow the tunable interferencefilter 5 to spectroscopically separate the Raman scattering light inresponse to the gas molecules to be detected. Then, when thespectroscopically separated light is received by the light receivingdevice 137, the light reception signal in response to the amount ofreceived light is output to the signal processing part 144 via thereceiver circuit 147.

The signal processing part 144 compares spectrum data of the Ramanscattering light in response to the gas molecules to be detectedobtained in the above described manner and data stored in a ROM,determines whether or not they are the target gas molecules, andidentifies the material. Further, the signal processing part 144 allowsthe display unit 141 to display the result information and outputs it tothe outside from the connection part 142.

In FIGS. 6 and 7, the gas detector 100 that performs gas detection fromthe spectroscopic separated Raman scattering light by spectroscopicseparation of the Raman scattering light using the tunable interferencefilter 5 has been exemplified, however, it may be used as a gas detectorthat identifies a gas type by detecting absorbance unique to the gas. Inthis case, a gas sensor that takes a gas inside and detects lightabsorbed by the gas of the incident lights is used as the optical moduleaccording to the invention. Further, a gas detector that analyzes anddiscriminates the gas flowing into the sensor using the gas sensor is anelectronic apparatus according to the invention. The configuration mayeven detect components of the gas using the tunable interference filteraccording to the invention.

Further, as a system for detection of the presence of a specificmaterial, not limited to the gas detection, but also a materialcomponent analyzer such as a non-invasive measurement device of sugarusing near-infrared spectroscopy or a non-invasive measurement device ofinformation of foods, living organisms, minerals, or the like may beexemplified.

Below, a food analyzer as an example of the material component analyzerwill be explained.

FIG. 8 shows a schematic configuration of a food analyzer as an exampleof an electronic apparatus using the tunable interference filter 5.Here, the tunable interference filter 5 is used, however, the tunableinterference filters 5A, 5B may be used.

As shown in FIG. 8, this food analyzer 200 includes a detector 210(optical module), a control unit 220, and a display unit 230. Thedetector 210 includes a light source 211 that outputs light, an imaginglens 212 that introduces light from an object to be measured, thetunable interference filter 5 that spectroscopically separates the lightintroduced from the imaging lens 212, and an imaging unit 213 (detectionunit) that detects the spectroscopically separated light.

Further, the control unit 220 includes alight source control part 221that performs turn-on and turn-off control and brightness control whenthe light source 211 is turned on, a voltage control part 222 thatcontrols the tunable interference filter 5, a detection control part 223that controls the imaging unit 213 and acquires spectroscopicallyseparated images imaged by the imaging unit 213, a signal processingpart 224, and a memory part 225.

In the food analyzer 200, when the system is driven, the light source211 is controlled by the light source control part 221, and the objectto be measured is irradiated with light from the light source 211. Then,the light reflected by the object to be measured passes through theimaging lens 212 and enters the tunable interference filter 5. A voltagethat enables spectroscopic separation of a desired wavelength is appliedto the tunable interference filter 5 under the control of the voltagecontrol part 222, and the spectroscopically separated light is imaged inthe imaging unit 213 including a CCD camera, for example. Further, theimaged light is accumulated as spectroscopically separated images in thememory part 225. Furthermore, the signal processing part 224 controlsthe voltage control part 222 to change the voltage value applied to thetunable interference filter 5, and acquires the spectroscopicallyseparated images for the respective wavelengths.

Then, the signal processing part 224 performs computation processing ondata of respective pixels in the respective images accumulated in thememory part 225, and obtains spectra in the respective pixels. Further,for example, information on components of foods with respect to thespectra is stored in the memory part 225. The signal processing part 224analyzes the data of the obtained spectra based on the information onthe foods stored in the memory part 225, and obtains food componentscontained in the object to be detected and their contents. Further, fromthe obtained food components and contents, food calories, freshness, andthe like may be calculated. Furthermore, by analyzing the spectrumdistributions within the images, extraction of apart in which freshnesshas been deteriorated in the food of the object to be inspected or thelike may be performed, and detection of foreign materials containedwithin the foods or the like may be performed.

Then, the signal processing part 224 performs processing to allow thedisplay unit 230 to display the information on the components, contents,calories, freshness, and the like of the foods as the object to beinspected obtained in the above described manner.

FIG. 8 shows the example of the food analyzer 200, however, a devicehaving nearly the same configuration may be used as the above describednon-invasive measurement device of other information. For example, thedevice may be used as a living organism analyzer that performs analysisof living organism components such as measurement, analysis, or the likeof body fluid components of blood or the like. The living organismanalyzer as a device for measurement of the body fluid components ofblood, for example, as a device for sensing ethyl alcohol, may be usedas a drunk driving prevention device that detects the influence ofalcohol of a driver. Further, the device may be used as an electronicendoscopic system including the living organism analyzer.

Furthermore, the device may be used as a mineral analyzer that performscomponent analyses of minerals.

In addition, the tunable interference filter, the optical module, andthe electronic apparatus according to the invention may be applied tothe following devices.

For example, by changing the intensity of the lights having respectivewavelengths with time, data can be transmitted by the lights havingrespective wavelengths. In this case, a light having a specificwavelength is spectroscopically separated by the tunable interferencefilter provided in the optical module and received by the lightreceiving unit, and thereby, the data transmitted by the light havingthe specific wavelength may be extracted. Optical communications may beperformed by processing the data of the lights having respectivewavelengths using an electronic apparatus having the optical module fordata extraction.

Further, as the electronic apparatus, the configuration may be appliedto a spectroscopic camera, a spectroscopic analyzer, and the like thatimage spectroscopically separated images by spectroscopic separation oflight using the tunable interference filter according to the invention.As an example of the spectroscopic camera, there is an infrared cameracontaining the tunable interference filter.

FIG. 9 is a diagram showing a schematic configuration of a spectroscopiccamera. As shown in FIG. 9, the spectroscopic camera 300 includes acamera main body 310, an imaging lens unit 320, and an imaging unit 330(detection unit).

The camera main body 310 is a part grasped and operated by a user.

The imaging lens unit 320 is provided in the camera main body 310 andguides entering image light to the imaging unit 330. Further, theimaging lens unit 320 includes an objective lens 321, an image forminglens 322, and the tunable interference filter 5 provided between theselenses as shown in FIG. 9.

The imaging unit 330 includes a light receiving device and images theimage light guided by the imaging lens unit 320.

In the spectroscopic camera 300, a light having a wavelength to beimaged is transmitted through the tunable interference filter 5, andthereby, a spectroscopically separated image of a light having a desiredwavelength may be obtained.

Furthermore, the tunable interference filter according to the inventionmay be used as a bandpass filter, and, for example, may be used as anoptical laser device that spectroscopically separates and transmits onlylights in a narrow band around a predetermined wavelength of the lightsin a predetermined wavelength range output by a light emitting deviceusing the tunable interference filter.

Further, the tunable interference filter according to the invention maybe used as a biometric identification device, and, for example, may beapplied to an identification device of blood vessels, finger prints,retina, iris, or the like using lights in the near-infrared range andthe visible range.

Furthermore, the optical module and the electronic apparatus may be usedas a concentration detector. In this case, the concentration of anobject to be detected in a sample is measured by spectroscopicseparation and analysis of infrared energy (infrared light) output froma material using the tunable interference filter.

As shown above, the tunable interference filter, the optical module, andthe electronic apparatus according to the invention may be applied toany device that spectroscopically separates a predetermined light fromincident lights. Further, as described above, the tunable interferencefilter according to the invention may spectroscopically separate pluralwavelengths by one device, and thus, measurement of spectra of theplural wavelengths and detection of plural components may be performedwith high accuracy. Therefore, compared to the device in the past thatextracts a desired wavelength using plural devices, downsizing of theoptical module and the electronic apparatus may be promoted and thetunable interference filter may preferably be used as a portable orvehicle-mounted optical device, for example.

In addition, the specific structures when the invention is implementedmay be appropriately changed to other structures within a range in whichthe purpose of the invention may be achieved.

The entire disclosure of Japanese Patent Application No. 2011-087225filed Apr. 11, 2011 is expressly incorporated by reference herein.

What is claimed is:
 1. A tunable interference filter comprising: a firstsubstrate; a second substrate opposed to the first substrate; a firstreflection film provided on a first reflection film fixing surface ofthe first substrate facing the second substrate; a second reflectionfilm provided on a second reflection film fixing surface of the secondsubstrate facing the first substrate and opposing the first reflectionfilm across a gap between the first and second reflection films; and afirst electrode provided on a first electrode surface of the firstsubstrate facing the second substrate, the first electrode surroundingthe first reflection film fixing surface in a plan view, and beingspaced apart from the first reflection film fixing surface in athickness direction of the first substrate, wherein the first electrodesurface is spaced apart from the second substrate by a differentdistance than the distance from the first reflection film fixing surfaceto the second substrate, the first reflection film covers a step betweenthe first reflection film fixing surface and the first electrodesurface, and a layered part in which the first reflection film and thefirst electrode are stacked is provided on the first electrode surface,the layered part being spaced apart from the second substrate by alarger distance than the distance from the first reflection film fixingsurface to the second substrate.
 2. A tunable interference filtercomprising: a first substrate; a second substrate opposed to the firstsubstrate; a first reflection film provided on a first reflection filmfixing surface of the first substrate facing the second substrate, thefirst reflection film fixing surface being surrounded by an annulargroove formed in the first substrate, and the first reflection filmoverlapping the first reflection film fixing surface and a portion ofthe annular groove; a second reflection film provided on a secondreflection film fixing surface of the second substrate facing the firstsubstrate and opposing the first reflection film across a gap betweenthe first and second reflection films; and a first electrode provided ona first electrode surface positioned within the annular groove of thefirst substrate facing the second substrate, wherein the first electrodesurface is spaced apart from the second substrate by a differentdistance than the distance from the first reflection film fixing surfaceto the second substrate, the first reflection film covers a step betweenthe first reflection film fixing surface and the first electrodesurface, and a layered part in which the first reflection film and thefirst electrode are stacked is provided on the first electrode surface,the layered part being spaced apart from the second substrate by alarger distance than the distance from the first reflection film fixingsurface to the second substrate.
 3. A tunable interference filtercomprising: a first substrate having a first part and a second part, thesecond part surrounding the first part; a second substrate that isopposed to the first substrate; a first reflection film that is disposedbetween the first part and the second substrate; a second reflectionfilm that is disposed between the first reflection film and the secondsubstrate; a first electrode that is disposed between the second partand the second substrate; and a second electrode that is disposedbetween the first electrode and the second substrate, wherein the firstpart is thicker than the second part, the first reflecting film and thefirst electrode are stacked at a layered part, and when viewed in adirection from the second substrate to the first substrate, the layeredpart is included on the second part.
 4. The tunable interference filteraccording to claim 1, further comprising: a second electrode provided ona second electrode surface of the second substrate facing the firstsubstrate, and opposing the first electrode, the second electrode beingspaced apart from the first electrode by a larger distance than the gapbetween the first and second reflection films, and the layered part isformed by extending the first reflection film from the first reflectionfilm fixing surface over the first electrode surface and stacking withan inner peripheral edge of the first electrode.
 5. The tunableinterference filter according to claim 1, wherein the layered part isformed by stacking the first reflection film on the first electrode. 6.The tunable interference filter according to claim 1, further comprisinga reflection film connection electrode connected to the secondreflection film.
 7. An optical module comprising: the tunableinterference filter according to claim 1; and a detection unit thatdetects light extracted by the tunable interference filter.
 8. Thetunable interference filter according to claim 2, further comprising: asecond electrode provided on a second electrode surface of the secondsubstrate facing the first substrate, and opposing the first electrode,the second electrode being spaced apart from the first electrode by alarger distance than the gap between the first and second reflectionfilms, and the layered part is formed by extending the first reflectionfilm from the first reflection film fixing surface over the firstelectrode surface and stacking with an inner peripheral edge of thefirst electrode.
 9. The tunable interference filter according to claim2, wherein the layered part is formed by stacking the first reflectionfilm on the first electrode.
 10. The tunable interference filteraccording to claim 2, further comprising a reflection film connectionelectrode connected to the second reflection film.
 11. An optical modulecomprising: the tunable interference filter according to claim 2; and adetection unit that detects light extracted by the tunable interferencefilter.
 12. The optical module according to claim 7, wherein the tunableinterference filter includes a reflection film connection electrodeconnected to the second reflection film, the optical module furthercomprising a voltage control unit that controls the reflection filmconnection electrode and the first electrode at the same potential. 13.An electronic apparatus comprising the optical module according to claim7.
 14. The optical module according to claim 11, wherein the tunableinterference filter includes a reflection film connection electrodeconnected to the second reflection film, the optical module furthercomprising a voltage control unit that controls the reflection filmconnection electrode and the first electrode at the same potential. 15.An electronic apparatus comprising the optical module according to claim11.